package com.kbt.util.tool;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;

/**
 * @author zhgk
 * @package: com.kbt.util.tool
 * @TODO: 生成惟一性32位GUID编码
 * @data: 2015/8/15 8:32
 * @version: V1.0
 */
public class UUIDUtilTool {


    private static Random myRand;
    private static SecureRandom mySecureRand;
    private static String valueBeforeMD5 = "";
    /*
     * Static block to take care of one time secureRandom seed.
     * It takes a few seconds to initialize SecureRandom.  You might
     * want to consider removing this static block or replacing
     * it with a "time since first loaded" seed to reduce this time.
     * This block will run only once per JVM instance.
     */
    private static String valueAfterMD5 = "";

    static {
        mySecureRand = new SecureRandom();
        long secureInitializer = mySecureRand.nextLong();
        myRand = new Random(secureInitializer);
    }

    /*
     * Method to generate the random GUID
     */
    private static void getRandomGUID(boolean secure) {
        MessageDigest md5 = null;
        StringBuffer sbValueBeforeMD5 = new StringBuffer();
        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            System.out.println("Error: " + e);
        }

        try {
            long time = System.currentTimeMillis();
            long rand = 0;

            if (secure) {
                rand = mySecureRand.nextLong();
            } else {
                rand = myRand.nextLong();
            }

            // This StringBuffer can be a long as you need; the MD5
            // hash will always return 128 bits.  You can change
            // the seed to include anything you want here.
            // You could even stream a file through the MD5 making
            // the odds of guessing it at least as great as that
            // of guessing the contents of the file!
            sbValueBeforeMD5.append(Long.toString(time));
            sbValueBeforeMD5.append(Long.toString(rand));
            valueBeforeMD5 = sbValueBeforeMD5.toString();
            md5.update(valueBeforeMD5.getBytes());
            byte[] array = md5.digest();
            StringBuffer sb = new StringBuffer();
            for (int j = 0; j < array.length; ++j) {
                int b = array[j] & 0xFF;
                if (b < 0x10) sb.append('0');
                sb.append(Integer.toHexString(b));
            }

            valueAfterMD5 = sb.toString();

        } catch (Exception e) {
            System.out.println("Error:" + e);
        }
    }

    /*
     * Convert to the standard format for GUID
     * (Useful for SQL Server UniqueIdentifiers, etc.)
     * Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6
     */

    /**
     * 生成非安全的UUID
     */
    public static String getUUID() {
        getRandomGUID(false);
        return valueAfterMD5.toUpperCase();
    }

    /**
     * 生成安全的UUID
     */
    public static String getSecreateUUID() {
        getRandomGUID(true);
        return valueAfterMD5.toUpperCase();
    }

//    /*
//      * Demonstraton and self test of class
//      */
//    public static void main(String args[]) {
//        for (int i = 0; i < 100; i++) {
//
//            System.out.println("Seeding String=" + UUIDUtilTool.valueBeforeMD5);
//            System.out.println("rawGUID=" + UUIDUtilTool.valueAfterMD5);
//            System.out.println("RandomGUID=" + UUIDUtilTool.getUUID());
//        }
//    }
}

